Factors Affecting Borsa İstanbul Trading Volume and Overconfidence Bias

Abstract

The aim of this study is to examine the factors affecting the trading volume of Borsa Istanbul within the framework of the overconfidence bias, one of the behavioral finance theories. For this purpose, stock market trading volume, BIST 100 index closing values, BIST 100 index historical volatility and credit default swaps (CDS) premium variables for the period covering the years 2010 – 2019 were used in the study. During the analysis process, firstly ADF, PP and KPSS unit root tests were performed and then Granger causality analysis was applied. The findings showed that the stock index and CDS premiums are the Granger cause of the trading volume, but volatility is not the Granger cause of the trading volume. The obtained findings were compared with the results in the literature and interpreted. It is interpreted that linking the earnings obtained with the increase in the stock market index to individual abilities, predictions and achievements may cause a tendency to overconfidence bias in investors. In addition, it is thought that this overconfidence may cause new transactions and thus an increase in the transaction volume. CDS premiums, on the other hand, give positive and negative signals about the future and are accepted as a risk indicator. It can be evaluated that investor who perceive risk as an opportunity and have a tendency to overconfidence bias will try to evaluate this situation with various positions and transactions and increase market trading volume. However, the fact that volatility is not the cause of trading volume can be explained by the perception that investors with high returns pay less attention to volatility and that their own forecasts are better than other investors' forecasting power. As a result, volatility is not effect the trading activity and investors focus on the value they have determined within the framework of overconfidence bias.